build: add xkbcommon include path
build: add xkbcommon include path

This is what we have on openSUSE nowadays:
$ pkg-config --cflags xkbcommon
-I/usr/include/pkg/libxkbcommon

rudimeier/xdotool,rudimeier/xdotool,rudimeier/xdotool,rudimeier/xdotool